It is known after drilling an oil or gas well to run tubing, known as casing, into the wellbore to act as a liner. The casing stabilizes the bore and prevents it from collapsing inwards. The casing is run into the newly formed bore from the surface, and the annular space between the casing and the bore is then filled with cement. The cement acts as a sealant and also to structurally support the casing.
It will be appreciated that before the casing is cemented in position it is important for the casing to be held substantially centrally in the bore. This allows a strong cement bond to be formed around the casing by ensuring that an even thickness is placed around the casing.
It is known to use centralizers to support the casing or liner away from the wellbore wall. Although there are several types of centralizer known in the art, one commonly used type is known as a solid centralizer. Solid centralizers are comprised of a hollow cylindrical body, often with a plurality of blades around the body. These blades are raised solid structures that extend longitudinally around the centralizer body and abut the wellbore wall to optimise stand off.
Centralizers are made from metal or plastics with each material offering its advantages and disadvantages. GB 2385342 describes a centralizer formed from both metal and plastics. The centralizer of GB 2385342 comprises a metal component that reinforces a main, plastics body of the centralizer. The metal component provides for reinforcement mainly in a direction radially of the centralizer bore.
I appreciated that the centralizer of GB 2385342 has shortcomings. More specifically, the centralizer of GB 2385342 can have a tendency, under certain circumstances, to break.